Photochemical properties of 1-(9-Anthryl)-2-(2-Quinolyl)ethylene

Spectral and photochemical properties of 1-(9-anthryl)-2-(2-quinolyl)ethylene (9A2QE) in neutral and protonated forms have been studied experimentally and by quantum-chemical methods. It has been found that the quantum yield of trans-cis photoisomerization (φ_tc) has values of φ_tc < 0.5 typical of the diabatic photoisomerization for both forms of 9A2QE. A comparison of this data with the results of the study of other aza-diarylethylenes containing the 2-styrylquinoline (2SQ) moiety has led to the general conclusion that the increase in the π-system in 2SQ upon fusion of the benzene rings results in the disappearance of the α-effect, which lies in the fact that the quantum yield increases upon going from the neutral to protonated form up to the values φ_tc > 0.5, which exceeds the limiting value for the diabatic photoisomerization.     

Spectral and photochemical properties of covalently linked dyads based on 2-styrylquinoline and 6-hydroxy-2-naphthoic acid

Photophysical and photochemical properties of bichromophoric covalently linked SnN dyads (n = 3, 5, 9), in which the 2-styrylquinoline (SQ) and 6-hydroxy-2-naphthoic acid (Np) moieties are linked by the dioxypolymethylene bridge–O–(CH₂)_n–O–have been studied. The properties of the dyads have been compared with those of the model compounds 2-(4-methoxystyryl)quinoline and methyl 6-hydroxy-2-naphthoate. Inductive-resonance (Förster) energy transfer (FRET) from the Np to the SQ unit with an efficiency up to 99.6% is observed in the S₁ state of the dyads. The Np unit in the neutral form does not affect the photoisomerization of the SQ unit regardless of the form of the latter, neutral or protonated (cationic). The Np moiety in the anionic (deprotonated) form hinders the photoisomerization of the SQ moiety, presumably, as a result to a combined action of several factors.     

Proton-controlled photoisomerization of 1-(2-pyridyl)-2-(2-quinolyl)ethylene

Quantum-chemical calculations (B3LYP/6-31G*) predict the formation of intramolecular hydrogen bond (IMHB) in the monoprotonated Z-isomer of 1-(2-pyridyl)-2-(2-quinolyl)ethylene (2P2Q), with this bond stabilizing the isomer relative to its E-counterpart. An experimentally observed increase in the quantum yield of trans-cis photoisomerization (φ_tc) by more than an order of magnitude (from 0.033 to 0.42 in acetonitrile) on passing from the neutral to the monoprotonated form of 2P2Q can be associated with IMHB, which manifested itself in the spectral properties of the Z-isomer. The IMHB breaks in the diprotonated form, and the value of φ_tc decreases back to the initial value. In addition to the photoisomerization, the photoreduction and photoaddition reactions of solvent molecules have been observed in an ethanol solution of 2P2Q.     

Photoisomerization of 2-styrylquinoline in neutral and protonated forms

The quantum yields of the trans-cis and cis-trans photoisomerization of 2-styrylquinoline (2SQ) and its several derivatives were measured in neutral, protonated, and quaternized forms. It was shown that electron-donor substituents in the styryl moiety increase the quantum yield of trans-cis photoisometization ?_tc in the neutral form as a result of stabilization of the intermediate zwitterionic perpendicular conformer. On passing from the neutral to the positively charged forms (protonated or quaternized), an increase in the quantum yields to ?_tc > 0.5 was observed, thus suggesting in terms of the classical diabatic mechanism of photoisomerization via the perpendicular conformer the shift of the minimum on the potential energy surface (PES) of the S ₁ state relative to the maximum of the S ₀ state PES to the cis-isomer or a possible contribution of the adiabatic route to the photoisomerization of the 2SQ cations.     

A quantum-chemical study of aza derivatives of (<Emphasis Type="Italic">E</Emphasis>)-1-styrylnaphthalene in the ground and lowest electronically excited states

The structures of (E)-1-styrylnaphthalene (1SN) and its aza derivatives 1-styrylisoquinoline (1SiQ) and 4- and 8-styrylquinolines (4SQ and 8SQ, respectively) in the neutral and protonated forms were calculated by the semiempirical (PM3) and DFT (B3LYP/6-31G*) methods. It follows from the DFT data that, in the ground state (S0), 1SiQ and 8SQ are planar, whereas 1SN, neutral 4SQ, and all protonated azastyrylnaphthalenes are nonplanar with aromatic cores twisted by 5 to 40° out of the plane of the double bond and with linear correlation between the torsion angles of the two cores. The calculated adiabatic excitation energy (E _ad) varies within 61–64 kcal mol^?1 for the neutral compounds and decreases for the protonated forms to 48, 45, and 33 kcal mol^?1 for 1SiQH⁺, 4SQH⁺, and 8SQH⁺, respectively. The lower E _ad value for 8SQH⁺ is in qualitative agreement with a lower photoisomerization quantum yield for this compound as compared with that for other protonated azastyrylnaphthalenes.     

Tautomerism of aza cycles: II. Synthesis and structure of 5-substituted 3-(2-hydroxyethylsulfanyl)-1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazoles and their salts. Preference of the 1H,4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazolium tautomers

New complexing agents, potentially tautomeric 3-(2-hydroxyethylsulfanyl)-1H-1,2,4-triazole, its 5-methyl-and 5-phenyl-substituted analogs, and some their salts, were synthesized, and their structure was discussed on the basis of the ¹H and ¹³C NMR, IR, and mass spectra, X-ray diffraction data, and published data. In keeping with the rule formulated previously for N-unsubstituted 1,2,4-triazoles having dissimilar substituents, the synthesized compounds were found to exist as 3-(2-hydroxyethylsulfanyl)-5-R-1H-1,2,4-triazole tautomers (3-R_A-5-R_D-1H-1,2,4-triazoly). They are protonated at the nitrogen atom in position 4 of the triazole ring. The ¹H and ¹³C NMR spectra of these compounds in trifluoroacetic acid suggest the presence of two forms due to equilibrium between the neutral and protonated species. Analysis of the crystallographic data for the triazolium salts and published data showed preference of the 1H,4H-1,2,4-triazolium tautomer.     

Synthesis and Structure of New 2-(2-Quinolyl)-1,3-tropolone Derivatives

4,6-Di-tert-butyl-3-nitro-1,2-benzoquinone reacts with substituted 2-methylquinolines to give the corresponding 2-(2-quinolyl)-4-nitro-1,3-tropolones and 2-(2-quinolyl)-1,3-tropolones.     

Synthesis,crystal structures,and antimicrobial activity of copper(II) and zinc(II) complexes derived from 2-bromo-4-chloro-6-[(2-morpholin-4-ylethylimino)methyl]phenol

An end-to-end azido-bridged dinuclear copper(II) complex [Cu₂L₂(μ_1,3-N₃)](NO₃) (I) and a mononuclear zinc(II) complex [ZnCl₂(HL)] ? CH₃OH (II), where L is 2-brom-4-chloro-6-[(2-morpholin- 4-ylethylimino)methyl]phenolate, have been prepared and characterized by elemental analyses, IR, and single crystal X-ray crystallographic determination (CIF files CCDC nos. 1415217 (I), 1415218 for (II)). The crystal of I is monoclinic: space group C2/c, a = 28.684(2), b = 7.1787(5), c = 18.292(1) Å, β = 117.887(3)°, V = 3329.1(4) ų, Z = 4. The crystal of II is monoclinic: space group P2₁/c, a = 10.8207(9), b = 12.3398(7), c = 14.9477(7) Å, β = 93.473(3)°, V = 1992.2(2) ų, Z = 4. The Schiff base ligand in I coordinates to the Cu atom through the phenolate O, imine N, and morpholine N atoms, while the Schiff base ligand in II coordinates to the Zn atom through the phenolate O and imine N atoms, with the morpholine N atom protonated. The effect of these complexes on the antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans was studied.     

Mass spectra of new heterocycles: XV. Fragmentation of 1-substituted 3-alkoxy-2-(propargylsulfanyl)- and 3-alkoxy-2-(allenylsulfanyl)-1<Emphasis Type="Italic">H</Emphasis>-pyrroles under electron impact

The electron impact mass spectra of 1-R-substituted 3-alkoxy-2-(propargylsulfanyl)- and 3-alkoxy-2-(allenylsulfanyl)-1H-pyrroles (R = Me, i-Pr, s-Bu, Ph) have been studied for the first time. These compounds give rise to stable molecular ions whose primary fragmentation follows three competing pathways: cleavage of the C–O bonds with expulsion of alkyl radical, cleavage of the C–S bonds with formation of [M–C₃H₃]⁺ ions, and cleavage of the C–N bonds with synchronous hydrogen transfer to give odd-electron [M–C_nH_2n]+ · ion. The main fragmentation pathway of 2-(propargylsulfanyl) derivatives is cleavage of the C–S bond with formation of [M–C₃H₃]⁺ ion.     

Synthesis,crystal structure,and antibacterial activity of oxovanadium(V) complexes derived from <Emphasis Type="Italic">N</Emphasis>'-[1-(5-fluoro-2-hydroxyphenyl)methylidene]nicotinohydrazide and <Emphasis Type="Italic">N</Emphasis>'-(5-fluoro-2-hydroxybenzylidene)-2-hydroxynaphthylhydrazide

Two new oxovanadium(V) complexes, [VOL¹(OCH₃)(CH₃OH)] (I) and [VOL²(OCH₃)] (II), where L¹ and L² are the di-anionic form of N'-[1-(5-fluoro-2-hydroxyphenyl)methylidene]nicotinohydrazide and N'-(5-fluoro-2-hydroxybenzylidene)-2-hydroxynaphthylhydrazide, respectively, have been synthesized and characterized by elemental analysis, FT-IR spectra, and single crystal X-ray determination (CIF files CCDC nos. 891852 (I), 891853 (II)). The crystal of I is monoclinic: space group P2₁/c, a = 8.061(1), b = 15.293(2), c = 13.471(2) Å, ß = 92.595(2)°, V = 1658.8(4) ų, Z = 4. The crystal of II is monoclinic: space group P2₁/n, a = 7.4454(9), b = 8.0833(9), c = 28.906(2) Å, ß = 92.644(2)°, V = 1737.8(3) ų, Z = 4. The V atom in I is in an octahedral coordination, and that in II is in a square-pyramidal coordination. The antibacterial activity of the compounds against various bacteria was assayed.     

Synthesis,Crystal Structure,and Antibacterial Activity of a Dinuclear Oxidovanadium(V) Complexes Derived from 2-[(2-Methylaminoethylimini)methyl]- 4-Trifluoromethoxyphenol

A new dinuclear oxidovanadium(V) complex, [V₂O₂(μ-O)₂L₂], where L is the monoanionic form of 2-[(2-methylaminoethylimini)methyl]-4-trifluoromethoxyphenol (HL), was prepared and characterized by IR, UV-Vis and ¹H NMR spectra, as well as single crystal X-ray diffraction (CIF file CCDC no. 1567062). The complex crystallizes as the monoclinic space group P2₁/c with unit cell dimensions a = 12.974(3), b = 6.572(2), c = 17.205(3) Å, β = 107.300(3)°, V = 1400.7(5) ų, Z = 2, R₁ = 0.0879, wR₂ = 0.1208, GOOf = 1.068. X-ray analysis indicates that the complex is a centrosymmetric dinuclear oxidovanadium(V) species with the V atoms in octahedral coordination. The Schiff base and the complex were evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescence) activities. The complex has the most activity against B. subtilis with the MIC value of 1.2 μg mL^–1.     

The crystal and molecular structure of Ni(II) complex with 1-(2-carboxyphenyl)-3-isopropyl-5-(benzimidazole-2-yl)formazane

The binuclear Ni(II) 1-(2-carboxyphenyl)-3-isopropyl-5-(benzimidazole-2-yl)formazanate (Ni₂L₂ · 2H₂O) (I) was synthesized and its crystal and molecule structures were determined by X-ray diffraction. Crystals I are triclinic: space group P \(\bar 1\), a = 7.4811(11), b = 10.8821(15), c = 11.4168(13) Å, α = 105.690(11) Å, β = 90.537(11) Å, γ = 93.166(11) Å, V = 893.2(2) ų, ρ(calcd.) = 1.581 g/cm³, Z = 1.     

Copper(II) complex with 2-(diphenylacetyl)indanedione-1,3: Synthesis and structure

A copper(II) complex with 2-(diphenylacetyl)indanedione-1,3 (HL) was synthesized. CuL₂·0.5C₄H₈O₂ crystals prepared from chloroform + 1,4-dioxane are triclinic, space group P \(\bar 1\), a = 15.0206(9) Å, b = 16.0132(9) Å, c = 16.8323(10) Å, α = 109.6850(10)°, β = 96.4390(10)°, γ = 97.7120(10)°, Z = 4. A unit cell contains two crystallographically independent centrosymmetric dinuclear complexes of the same structure. Each copper(II) atom is coordinated by bidentate cis-oriented deprotonated ligands L at the corners of the square. Bridging 1,4-dioxane molecules make the CN of each metal atom five.     

Synthesis, characterization and electroluminescence of B(III) compounds: BPh2(2-(2-quinolyl)naphtho[b]imidazolato) and BPh2(2-(2-quinolyl)benzimidazolato)

Two novel luminescent boron compounds, BPh₂(2-(2-quinolyl)naphtho[b]imidazolato) (1) and BPh₂(2-(2-quinolyl)benzimidazolato) (2), have been synthesized by the reactions of triphenylboron with appropriate ligands, 2-(2-quinolyl)naphtho[b]imidazole (QNI) and 2-(2-quinolyl)benzimidazole (QBI), respectively. The structure of 1 was determined by single crystal X-ray diffraction, while 2 by spectroscopic methods. The structure of 1 reveals that the boron center is four coordinated. Several types of OLED possessing different colors were fabricated by using 1 as emitter. For the three-layer OLED with the structure ITO/NPB/2/Alq₃/Mg-Ag, an emission band covering the whole visible region from 400 to 750 nm with the maximum brightness of 320 cd/m² was observed, indicating a perfect white light OLED (CIE = 0.33, 0.37). Compounds 1 and 2 form a new family of organometallic emitting materials which could be of interest for practical application.     

Synthesis,characterization, crystal structures,and antimicrobial activity of cobalt(II) and iron(III) complexes derived from N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide

A new cobalt(II,III) complex, [Co^IIIL₂]₂[Co ₂ ^II (HL)₂(OH₂)₂(CH₃OH)₂] ? 2H₂O (I) and a new iron(III) complex, [Fe^III(HL)₂](NO₃) (II), where L^2– and HL^– are the dianionic and monoanionic form of N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide, respectively, have been prepared and characterized by elemental analyses, infrared and UV-Vis spectroscopy and single-cyrstal X-ray diffraction (CIF files CCDC nos. 1417971 (I), 1417979 (II)). Complex I crystallizes in the monoclinic space group P2₁/n with unit cell dimensions a = 16.1665(9), b = 14.5692(8), c = 19.086(1) Å, β = 96.347(1)°, V = 4467.9(4) ų, Z = 2, R ₁ = 0.0521, and wR ₂ = 0.1411. Complex II crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a = 12.475(1), b = 12.202(1), c = 18.859(2) Å, V = 2870.8(4) ų, Z = 4, R ₁ = 0.0796, and wR ₂ = 0.1981. The metal atoms in the complexes are in octahedral coordination. Crystals of the complexes are stabilized by hydrogen bonds. The efficiency of the aroylhydrazone and the two complexes was evaluated against B. subtilis, S. aureus, E. coli, P. fluorescence, C. albicans and A. niger, with the complexes demonstrating enhanced activity relatively to the free ligand.     

3-(4-fluorophenyl)-1<Emphasis Type="Italic">H</Emphasis>-pyrazole-4-carbaldehyde in the synthesis of aza-and diazaphenanthrene derivatives

Condensation of 3-(4-fluorophenyl)-1H-pyrazole-4-carbaldehyde with 2-naphthyl-or 6-quinolylamine and CH-acids (acetone, acetophenone, cyclic mono-and β-diketones) provided new derivatives of benzo[f]quinoline, benzo[a]phenanthridine, benzo[a]acridine, and 4,7-phenanthroline. The arising in the course of the reaction [3-(4-fluorophenyl)-1H-pyrazole-4-ylmethylene]-2-naphthyl-(or 6-quinolyl)amines, [3-(4-fluorophenyl)-1H-pyrazole-4-ylmethylene]-1,3-indandione, and octahydro-1,8-xanthenedione derivatives were isolated.     

Fragmentation of Protonated <Emphasis Type="Italic">N</Emphasis>-(3-Aminophenyl)Benzamide and Its Derivatives in Gas Phase

An ion of m/z 110.06036 (ion formula [C₆H₈NO]⁺; error: 0.32 mDa) was observed in the collision induced dissociation tandem mass spectrometry experiments of protonated N-(3-aminophenyl)benzamide, which is a rearrangement product ion purportedly through nitrogen-oxygen (N–O) exchange. The N–O exchange rearrangement was confirmed by the MS/MS spectrum of protonated N-(3-aminophenyl)-O ¹⁸ -benzamide, where the rearranged ion, [C₆H₈NO ¹⁸ ]⁺ of m/z 112 was available because of the presence of O ¹⁸ . Theoretical calculations using Density Functional Theory (DFT) at B3LYP/6-31 g(d) level suggest that an ion-neutral complex containing a water molecule and a nitrilium ion was formed via a transition state (TS-1), followed by the water molecule migrating to the anilide ring, eventually leading to the formation of the rearranged ion of m/z 110. The rearrangement can be generalized to other protonated amide compounds with electron-donating groups at the meta position, such as, –OH, –CH₃, –OCH_3, –NH(CH₃)₂, –NH-Ph, and –NHCOCH₃, all of which show the corresponding rearranged ions in MS/MS spectra. However, the protonated amide compounds containing electron-withdrawing groups, including –Cl, –Br, –CN, –NO₂, and –CF₃, at the meta position did not display this type of rearrangement during dissociation. Additionally, effects of various acyl groups on the rearrangement were investigated. It was found that the rearrangement can be enhanced by substitution on the ring of the benzoyl with electron-withdrawing groups.

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2-Propylamino-5-[4-(2-hydroxy-3,5-dichlorobenzylideneamino) phenyl]-1,3,4-thiadiazole: X-ray and DFT-calculated structures

2-Propylamino-5-[4-(2-hydroxy-3,5-dichlorobenzylideneamino) phenyl]-1,3,4-thiadiazole, formulated as C₁₈H₁₆Cl₂N₄OS (I), was synthesized. The crystal and molecular structure of (I) have been determined by ¹H-NMR, IR, and X-ray single crystal diffraction. The compound (I) crystallizes in the monoclinic, space group P2(1)/c with unit cell parameters a = 9.0576(2) Å, b = 24.3382(8) Å, c = 9.0585(2) Å, M _r = 407.31, V = 1851.13(9) Å³, Z = 4, R ₁ = 0.036, and wR ₂ = 0.096. Molecular geometry from X-ray experiment of (I) in the ground state has been compared using the density functional method (B3LYP) with 6-31G(d) basis set. To determine conformational flexibility, molecular energy profile of (I) was obtained by semi-empirical (PM3) calculations with respect to selected degree of torsional freedom, which was varied from ?180° to +180° in steps of 10°. The results are indicative that the Schiff base, which contains a thiadiazole ring, prefers to be in E-configuration. In addition, molecular electrostatic potential, frontier molecular orbitals, and natural bond orbitals analysis were performed by the B3LYP/6-31G(d) method.     

Synthesis and crystal structure of Fe(III) and Al(III) complexes with 2-diphenylacetyl-1,3-indandione

Iron(III) and aluminum(III) complexes with 2-diphenylacetyl-1,3-indandione (HL) have been synthesized. The structures of the obtained compounds FeL₃(I) and AlL₃(II) were studied. The isostructural crystals are monoclinic, I: Z = 8, space group P2_1/c, a = 16.061(3) Å, b = 16.658(3) Å, c = 22.015(4) Å, β = 111.41(3)°; II: Z = 8, space group P2_1/c, a = 16.115(14) Å, b = 16.476(8) Å, c = 21.949(20) Å, β = 111.04(11)°. The structural units of crystals I and II are neutral molecules in which each ligand is bidentately coordinated to a central metal atom through the oxygen atom of the acyl keto group and an oxygen atom of the indandione fragment to form a six-membered chelate ring. In the crystals, neutral molecules I and II form pseudodimers due to stacking of indandione moieties of two adjacent coordination spheres and additional C-H…O contacts. Each pseudodimer is in contact with six neighboring dimers also through hydrogen bonds C-H…O to form an infinite framework.     

Nickel(II) complex with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane

A nickel(II) complex, [Ni(taetacn)](ClO₄)₂ ? H₂O, where taetacn = 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane was synthesized. The crystal structure was determined by the single-crystal X-ray diffraction method at 293 K. The complex crystallizes in the orthorhombic space group Pna2₁ with a = 16.004(2) Å, b = 10.186(1) Å, c = 13.937(2) Å, V = 2271.9(5) ų, D_x = 1.56 g cm^?3, D_m = 1.59 g cm^?3 (floatation method), and Z = 4. The R₁ [I > 2σ(I)] and wR₂ (all data) values are 0.0636 and 0.1672, respectively, for all 4845 independent reflections. The compound is composed of octahedral nickel(II) cation with three 2-aminoethyl pendant groups of taetacn, tetrahedral ClO ₄ ^? anion, and a water molecule of crystallization. Electronic spectra are consistent with the octahedral geometry. Temperature dependence of the magnetic susceptibility (4.5–300 K) can be interpreted considering the zero-field splitting of the nickel(II) ion (g = 2.14, D = 3.72 cm^?1, and Nα = 300 × 10^?6 cm³ mol^?1). Cyclic voltammetry in DMF showed quasi-reversible and irreversible oxidation waves (E_pa = 0.54 V, E_pc = 0.45 V; E_pa = 1.16 V, E_pc = 0.71 V vs. Ag/Ag⁺).